SMS, or text messaging, is a communications protocol that allows users to send and receive short text messages using mobile devices such as cellular phones, smartphones or personal digital assistant (PDA) [4,5]. The message can be composed of a combination of alphanumeric characters that form words or meaningful truncation of words. However, SMS has a limitation of being able to transmit only a maximum of 160 characters, including spaces .
SMS delivers messages in a store and forward manner, essentially similar to paging. Instead of being sent directly to the receiving mobile device, a text message is temporarily stored in a central short message center (SMC), which then forwards the message to the intended recipient. This is useful since a message can still be received at a later time even if the recipient phone is turned off or out of coverage during the time of sending [5,6].
The intense development and widespread use of SMS worldwide has broadened the possible applications of this service. From a simple medium that can convey short communications between two or more persons, SMS is used nowadays for information dissemination services (i.e. news, weather, stock market, and entertainment), mobile banking, internet/email notifications, mobile chatting, and even catechism [5,6,7].
Despite the limitations of size and a not so easy input mechanism through the phone keypad, SMS is still a very popular technology that has a lot of promising applications that are waiting to be developed and deployed.
Text Messaging and the Philippines
Text messaging in the Philippines has been phenomenal and its use is exponentially increasing over the years . “Filipino cell phone users have truly developed a culture of texting after the Philippines retained its title as the ‘text – messaging-capital-of-the-world’ – sending a remarkable 1.39 billion text messages from a subscriber base of just 50 million .”
The appeal of the SMS technology to Filipinos may be attributed to the economic state of most mobile phone users. In the Philippines, a text message would cost only Php 1.00 (approximately US$0.02) while a 1minute prepaid voice call costs around Php 8.00 (approximately US$0.16). Because of this, “more than 90 per cent of the country’s thirty-five million subscribers” resort to SMS as a primary means of communicating with others. It is estimated that a subscriber sends about seven text messages per day. 
Historically, text messaging was a free service from its inception in 1994 until 2000 . Despite the current low rate of a mere peso for every text message, mobile networks devise promotional offers wherein subscribers will only spend Php 30.00 (approximately US$0.62) to be able to send unlimited text messages for one to two days. Due to the affordability of text messaging, “the Philippines has become the first country in the world where mobile users spend more on data services than on voice, according to a leading research company .”
SMS and Health
The widespread use of text messaging in various financial and entertainment applications triggered the health care community to take advantage of this technology for health services delivery. In recent years, various SMS applications for health have been utilized both by health practitioners and their patients.
Most SMS health applications focus on health information dissemination. In England, text message reminders are sent to women to prompt them to take their oral contraceptive pills. A SMS reminder system for AIDS patients in Australia was shown to improve patient compliance to the complex combination of drugs. Supportive text messages that supplement smoking cessation programs in New Zealand were found to be valuable in encouraging smokers to quit. Finally, the Health Department of San Francisco, California use text messaging to disseminate sexual-health information to adolescents and young adults. [12,13]
Despite the potential applications of text messaging in health, there are some instances wherein it may not be a suitable medium for delivering messages, such as when disclosing to a patient a critical diagnosis like cancer or AIDS . In these cases, a face to face encounter with the patient is the most appropriate and ethical way of conveying the message.
The SMS Telemedicine Program was formally launched last 15 October 2007 through a Memorandum of Agreement signed between the UPM-NThC and the DOH during the Continuing Medical Education (CME) Conference of the DttB Program at Cagayan de Oro City, Philippines. A total of 34 DttBs from various remote villages of the Philippines participated in this program. The DttBs were asked to sign an agreement that the information which they will receive are opinions of the DEs and that the final diagnosis and management for the patient shall remain their responsibility. To remove the financial barrier for these doctors, the UPM-NThC gave each doctor a monthly Php100.00 (approximately US$ 2.00) credit load in order to refer their cases to the Center.
The doctors were encouraged to refer at least one case per week regarding any domain. The Center gave them the option to send their clinical referrals via text message to any of the two network mobile numbers (Globe and Smart). In instances where they do not have any problematic cases to refer, they were asked to send a census of all the cases they saw during the previous week. Only non-emergency cases were to be accepted since the Center can only guarantee a turn-around time of up to 48 hours.
During the May 2008 CME Conference of the DttBs, an additional 21 doctors signed up, making a total of 55 DttBs included in the pilot program.
Central Operations Procedure
The SMS Telemedicine Program is managed by a Telehealth Physician, two Telehealth Nurses, and seventeen DEs from various specialties.
The text messages were received by the Telehealth Nurses who triaged the cases to the appropriate DEs. In cases where they have difficulty in classifying the referral, they elevate it to the Telehealth Physician. The text messages were sent to the DEs through the modality that they chose. Some preferred to receive text messages through their cellular phones, while others opted to receive an email containing all the referrals for the day. All the DEs were alerted via SMS for any incoming referrals addressed to them. Once the referrals were answered by the DEs, the Telehealth Nurse forwarded the replies to the inquiring DttB.